Oxidation of aldehydes



V, UNITED srA'rEs PATENT OFFICE of crotonic acid by oxidation processes involving In passing through the solution it also effectively heretofore employed are not as efllcient as may acted crotonaldehyde, the distillation being prefmay be oxidized to crotonic acid in high yield and most obtained.

Patented Nov. 8, 1949 i I I I 2,487,188 OXIDATION OF ALDEHYDES George W. Seymour, Blanche B. Whl and Ellsabeth Bareback, Cumberland, Md, 8881mm tov Corporation of America, a-eerporatlon o ware No Drawing. Application May 19, 1.845,

Serial No. 594,789

4 Claims. (Cl. 2 -530) l I 2 This invention relates to an improved process tion. To prevent the freezing of the glacial acetic for the production of organic acids, and relates acid diluent, we preferably add from 10 to more particularly to the preparation of crotonic by weight of crotonaldehyde thereto prior to acid from crotonaldehyde by an improved catcooling and before the major portion is added alytic oxidation process.- 5 to the reaction mixture. The gaseous oxygen is An object of this invention is the preparation preferably introduced in a finely-divided form.

the catalytic, liquid phase oxidation of crotonalmaintains the same under continuous agitation. .dehyde. The passage of oxygen through the solution is Another object of this invention is the produc- 1 continued, after all of the crotonaldehyde has tion of crotonic acid, by the oxidation of crobeen addedand completion 'fthe oxidation reactonaldehyde, in improved yield and of a satisfaction is observed by a change in color of the solutory degree of purity with the minimum formation undergoing catalytic oxidation, the change tion of undesirable aldehydic polymerization in color being from brown to green. This change products. 15 is usually observed after from 48 to 72 hours de- Other objects of this invention will appear from pending upon the rate at which the crotonaldethe following detailed description. hyde is added, the degree of dispersion of the Croton'aldehyde may be oxidized to the correadded oxygen and the degree of agitation. The spending unsaturated acid in accordance with reaction mixture obtained is then fractionated various well-known procedures. The processes to remove the acetic acid diluent and any unrebe-desired since the unsaturated character of the erably effected rapidly under reduced pressure crotonaldehyde renders it susceptible to the forand at a low temperature, e. g. at a pressure of 15 mation of undesirable polymerization products to mm. of mercury and temperatures'of 20 to during reaction. When conducting the oxidation 25 35 C. After removal of the diluent and unreon a relatively small laboratory scale, the formaacted crotonaldehyde, crude crotonic acid crystaltion of these undesirable polymerization products lizes out in the residue. The crude crystals may is not very serious. On a commercial scale, howthen be purified by recrystallization from hot ever, the elimination of these side reactions bewater. Purified crotonic acid may be obtained come exceed n y impor nt if t y ld o n in yields of 40 to 80% of theoretical in accordance is to be satisfactory. with our process. Where temperature control is We have now discovered that crotonaldehyde not maintained, yields of only 20 to 30% are at with substantially decreased polymer formation if the oxidation is eflected with free oxygen at a pl temperature of 5 to 10 C. in glacial acetic acid as 2 Its b w ht of a of man anese a diluent, employing manganese salts as a catalyst gg' g g fg fg m to aid the oxidation portion of 6.6 parts of manganese acetate to 1 part Preferably, the catalyst employed comprises a of potassium permanganate are dissolved in 1000 mixture of manganese acetate and potassium pere 40 parts by weight of glacial acetic acid and the maneanete in a ratio 5 to 7 Parts by Weight solution obtained cooled to 5 to 8" c. To the manganese acetate to each Part by weight of cooled solution, contained in a suitable vertical 5955mm Permanganate'the catalyst mixture being vessel of cylindrical shape, are gradually added employed in a concentration of 0.1 to 0.2% by 3 parts by weight of crotonaldehyde Shnu1 weight based on the glacial acetic acid diluent in taneously t t introduction of the t w i h h oxidation is eflectedaldehyde, oxygen is circulated through the solu- In accordance with our process, e prefer o tion in finely divided form, the oxygen being eneflect the oxidation of crotonaldehyde to crotonic t t t base of t vessel through a a i y dissolving the e red m n f antered glass plate. The latter permits the passage ganese salts as catalyst in from 500 150 1000 parts of the gaseous oxygen but only in the form of by weight of glacial acetic acid. in h l very fine bubbles. The introduction of the oxytion to 5 to 10 C. nd. while r ly n c011- gen through the sintered glass plate is continued 1 111 1 137 a n predetermined amount of along with the addition of crotonaldehyde, for a crotonaldehyde thereto, e. g. from 400 to 800 parts total of 72 hours while maintaining the temperaby weight, bubbling dry oxygen through the soluso ture at 5 to 8 C. The color of the reaction mixture changes from brown to green when oxidation is completed.

The acetic acid and unreacted crotonaldehyde are then distilled oil at 28 C. under a pressure of 25 mm. of mercury and the crude crotonic acid crystallizes out. The crude acid is purified by recrystallization in hot water and 200 parts acid are obtained. crotonic acid obtained represents a yield of 78% of theoretical on the crotonaldehyde reacted. The unreacted crotonaldehyde and the acetic acid diluent recovered during distillation may be recycled in the process, the crotonalde-. hyde present serving to prevent solidification oi the acetic acid at the low temperature employed for oxidation. The recycled crotonaldehyde is, of course, subject to oxidation together with the crotonaldehyde later added during the course of the reaction. The oxidation reaction may be made substantially continuous by employing dual oxidation reaction vessels or chambers and alternately effecting the desired oxidation in the respective chambers.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention what we desire to secure by Letters Patent is:

1. Process for the production of crotonic acid, which comprises catalytically oxidizing crotonaldehyde by forming a solution of glacial acetic acid containing from 10 to 15% by weight of crotonaldehyde, cooling the solution to to 0., adding the remainder of the crotonaldehyde to the reaction mixture and then passing free, gaseous oxygen through a solution of crotonalde-- hyde in glacial acetic acid maintained at a temperature of from 5 to 10 C., the oxidation catalyst employed comprising a mixture of manganese acetate and potassium permanganate.

2. Process for the production of crotonic acid, which comprises catalytically oxidizing crotonaldehyde by forming a solution of glacial acetic acid containing from 10 to by weight of crotonaldehyde, cooling the solution to 5 to 10 0., adding the remainder of the crotonaldehyde to the reaction mixture and then passing free, gaseous oxygen through a solution of crotonaldehyde in glacial acetic acid maintained at a temperature of from 5 to 10 C., the oxidation catalyst employed comprising 0.1 to 0.2% by weight of the glacial acetic acid, of a mixture of manganese acetate and potassium permanganate.

3. Process for the production of crotonic acid,

catalyst employed comprising 0.1

which comprises catalytically oxidizing croton- 4 aldehyde by forming a solution of glacial acetic acid containing from 10 to 15% by weight oi crotonaldehyde, cooling the solution to 5 to 10' C., adding the remainder of the crotonaldehyde to the reaction mixture and then passing iree, gaseous oxygen through a solution of crotonaldehyde in glacial acetic acid maintained at a temperature of from 5 to 10 C., the oxidation to 0.2% by weight of the glacial acetic acid, of a mixture of manganese acetate and potassium permanganate in the ratio of 5 to 7 parts by weight of manganese acetate to each part of sodium permanganate.

4. Process for the production of crotonic acid, which comprises catalytically oxidizing crotonaldehyde by forming a solution of glacial acetic acid containing from 10 to 15% by weight of crotonaldehyde, cooling the solution to 5 to 10' 0., adding the remainder of the crotonaldehyde to the reaction mixture and then passing free, gaseous oxygen through a solution of crotonaldehyde in glacial acetic acid maintained at a temperature 01' from 5 to 10 0., the oxidation catalyst employed comprising 0.1 to 0.2% by weight of the glacial acetic acid, of a mixture 0! manganese acetate and potassium permanganate in the ratio of 5 to 7 parts by weight of manganese acetate to each part of sodium permanganate, distilling of! unreacted crotonaldehyde and acetic acid from the reaction mixture while maintaining the said reaction mixture under a pressure of 15 to 25 mm. of mercury and separating crotonic acid therefrom.

GEORGE W. SEYMOUR. BLANCI-IE B. WHITE. ELISABETH BARABASH.

REFERENCES CITED The following references are of record in the Number Name Date 1,445,544 Odinga Feb. 13, 1923 2,183,325 Staudinger Dec. 12, 1939 2,212,900 Groll et al. Aug. 27, 1940 2,377,584 Staudinger et al. June 5, 1945 2,386,365 Staudinger et a1. Oct. 9, 1945 FOREIGN PATENTS Number Country Date 165,728 Great Britain Sept. 27, 1922 369,636 Germany Feb. 22, 1923 OTHER REFERENCES Duchesne et al., Bull. soc. Chim. (Paris), vol. 35, Pp. 1311-1316 (1924). 

